The electoral difficulties facing the 51-year-old son of one of the state's best-known political personalities, the late Gov. Bob Casey Sr., have not evaporated. And November's election is still light-years away in political time.
But a combination of circumstances - a slightly improving economy, his own higher profile in recent months, and a crowded field of Republican challengers - has contributed to Casey's rosier outlook.
"No Republican congressmen or prominent statewide officials stepped in to run against Casey this time," said Democratic strategist Larry Ceisler in Philadelphia. "That speaks more to how Republicans feel about his vulnerability than anything else."
Casey's approval ratings now hover at 47 percent, according to a poll of 800 likely Pennsylvania voters released earlier this month by Susquehanna Polling & Research. At the same time, nearly a third of respondents said they were still undecided after the senator's five years in office.
The GOP hopes to capitalize on that uncertainty.
Five candidates are vying for the party nomination, including a Chester County entrepreneur, a former gubernatorial candidate, and a Western Pennsylvania coal executive.
Though none has emerged as a front-runner, each brings an arsenal of attacks on what the candidates like to label the "Obama-Casey agenda."
"I don't think your spot in the gene pool should be a qualification for the United States Senate," said Steve Welch, the Malvern entrepreneur whom GOP state committee members endorsed last month at the urging of Gov. Corbett.
For his part, Casey hopes to make one thing clear: He's running on his own merits. Not Obama's, not his father's.
The senator was not available for a telephone interview for this article, his aides said.
"I have a strong record of supporting job creation, fighting unfair foreign trade, and leading the effort to extend the payroll-tax cut," Casey said in an e-mail. "I always put the interests of Pennsylvania first."
Throughout his first term, Casey has emerged as an economic progressive with moderate to conservative social views. He is among that small rank of Democratic officeholders who have spoken out against abortion rights.
He helmed the Senate's foreign policy subcommittee on Middle East affairs and took a lead role on bills dealing with congressional ethics, extending child health-insurance programs, and stopping Internet piracy.
Missing from that list, Republicans say, are many of the weightiest issues facing the country in the last five years.
Dubbed "Sen. Zero" by his challengers, Casey, they say, has largely steered clear of outspoken stances such as those that distinguished his predecessor, Rick Santorum, who emerged as a national culture warrior during the early 2000s and is now a presidential candidate.
Casey "has one of the most famous names in Pennsylvania, but most people can't really tell you what he's done," said Mike Barley, executive director of the state Republican committee. "His approval ratings are about a mile wide and an inch deep."
As though mindful of the need to raise his profile, Casey has propelled himself to higher visibility of late. In the last month alone, he has visited with union members from Delaware County refineries slated for closing, and claimed credit for securing federal aid for Delaware River dredging. He even made headlines Friday by calling for the FBI to join an investigation into the disappearance of a Western Pennsylvania girl missing since 1958.
Of greater import was the vocal role Casey played on the bipartisan congressional committee that struck a payroll-tax-cut compromise last week - an issue Obama has identified as a priority of his administration.
In December, Casey was lead sponsor of the initial version of the bill to extend the cut. He later dropped his proposal to partially fund the extension by raising taxes on millionaires - a retreat he characterizes as a successful bipartisan gesture.
His Republican rivals, however, were quick to try to turn those efforts against him.
"The payroll-tax situation was an absolute gimmick," said Marc Scaringi, a Republican lawyer and former Santorum aide now vying for the seat held by his former boss. "Sen. Casey has been pretending to be a tax cutter on an insignificant issue driven by Obama."
For Obama early
The senator emerged as one of candidate Obama's first and most-outspoken advocates in Pennsylvania in 2008, and has voted more often than not with the White House on issues such as health care and economic-stimulus packages. Ever since, the two Democrats' fortunes in public opinion polls have risen and fallen in tandem.
But in what some suggest is a bid to show his independence - or to protect himself from voters angry with Obama - Casey has drawn attention to votes in the last year that differed from the president's stances on foreign trade deals and the country's approach to Iran's nuclear intentions.
Earlier this month, Casey, a Catholic, came out against the White House's controversial plan to require religious-affiliated employers such as hospitals and colleges to pay for contraception in their health-care plans.
"We don't agree on other issues," Casey added. "I have a record of working with Republicans and Democrats, because that is the best way to get things done."
Tom Smith, a Republican candidate and former coal executive, described such distancings as too little, too late.
"We need an active leader," he said, "not someone who is always going to follow the president's lead."
With a little more than two months to go until the April 24 primary, exactly who will pick up the GOP standard remains uncertain.
The Republican State Committee in January endorsed Welch, setting off a wave of dissent among the party's grassroots groups, who objected to the role Corbett played in "forcing his choice" upon them.
Welch, who built his business bona fides on two successful technology firms, has faced criticism for his past as a registered Democrat - a choice he defends by arguing that the GOP strayed from its ideals during the George W. Bush years.
"I came running back as soon as I saw where the Obama-Casey-Pelosi agenda was taking us," Welch said.
Among more conservative members of the party, former State Rep. Sam Rohrer of Berks County has emerged as a strong contender with a tea party-friendly platform and a strong showing in debates. (He is also the only GOP candidate with experience as an elected officeholder.) Rohrer gained wider name recognition in the 2010 gubernatorial primary when he challenged then-Attorney General Corbett from the right.
"My political experience brings a practical, proven record with predictability of how I will approach the breadth of issues," he said.
Smith, too, could pose a viable challenge to Welch. So far, his $4.5 million campaign fund - much of it his own money - makes him the only GOP candidate to boast a larger war chest than Casey's $4.4 million total.
But Smith, like Welch, has a political past that dismays some conservatives. In 2010, he served as an Armstrong County Democratic committee member, but, he is quick to point out, he was booted from the post for supporting GOP candidates.
Bucks County veterans' advocate David Christian, a decorated Vietnam veteran, also remains in the race.
A longshot Democratic primary challenger, Allegheny County spring manufacturer Joseph Vodvarka, is also on the ballot.
So far, little independent polling exists to show whether any of the Republican candidates have edged ahead of the pack. More than 70 percent of likely Republican primary voters remain undecided on their pick this spring, according to a Susquehanna Poll released last week.
Rohrer and Smith held a slight edge over their rivals - with 10 percent and 8 percent shares, respectively. Welch hovered at 2 percent, and Christian and Scaringi each held 1 percent.
"We haven't even dared poll," said Chris Borick, a pollster and political science professor at Muhlenberg College. "Nobody knows who these guys are."
And when you are running against one of the best-known names in Pennsylvania politics, that can only work to your disadvantage.
Contact staff writer Jeremy Roebuck at 267-564-5218, firstname.lastname@example.org,
or @jeremyrroebuck on Twitter.