PIERRE, S.D. — U.S. Sen. John Thune said Tuesday that he won't join what's expected to be a crowded GOP field of presidential hopefuls next year, concluding he would have a difficult time fundraising and that President Barack Obama would be tough to beat.
Thune, R-S.D., was seen as one of several potential challengers to Obama in 2012. His exit is the first clear signal of who will — and who will not — compete for the Republicans' nomination.
The 50-year-old Thune isn't well-known among national voters, but some Republican operatives saw him as a can-do, common-sense alternative with a Midwestern aura and strong conservative credentials. The most optimistic suggested Thune could become a Republican Obama — a younger politician whose style could inspire voters looking for change.
Thune said he was deterred by several obstacles: fundraising, name recognition and a tough incumbent.
"We would have a more difficult time with the resources than perhaps some other better-known candidates would have," he said.
Thune also called Obama a "very shrewd politician" who was moving toward the center after last year's midterm elections to pass a tax-cut extension with Republican support.
"As I observed his response and reaction to the midterm election, that was all part of my assessment of the landscape," he said. "Any incumbent is a tough race, and he's no exception. I think he's got plenty of vulnerabilities, but I also observed how adept politically he was."
Thune's comments about Obama's political strength could anger Republicans eager to make the Democrat a one-term president. His comments acknowledge the GOP's uphill climb against an incumbent president and masterful campaigner who never really shut down his political machine.
The right Republican could beat Obama, who faces the prospect of voter anger over government spending, Thune said. He declined to name potential candidates he sees as good bets.
Thune told the AP he ultimately decided not to run because he wanted to stay in the Senate.
"I didn't feel that I could proceed with a national campaign and continue to do the kind of justice I needed to do for my day job," he said.
Obama campaigned for the presidency from the Senate. He was not part of his party's leadership, however. Thune is now the No. 4 Republican in the Senate and the chairman of the Senate Republican Policy Committee.
More than a dozen potential GOP candidates still are weighing presidential bids. The fractured field reflects an uncertainty among Republicans about which message is best to adopt as they prepare to face off against Obama.
Fiscal conservatives, social conservatives and tea party-style activists all are working to help preferred candidates. Yet no one has managed to appeal to all three pieces of the primary electorate struggling with questions about party purity and concerns about electability.
Thune grew up in small-town South Dakota and captured the national spotlight in 2004 after beating Democrat Tom Daschle, then the Senate Minority Leader, in a tight race. He won re-election last November without an opponent.
Thune is popular among Republican lawmakers, and though none had endorsed him, he was the lone member of the Senate laying groundwork for a potential bid.
He seemed interested in a national profile.
Last year, he keynoted the Republican National Committee's summer meeting for state chairmen and executive directors, and started calling through key activists in the early nominating states of Iowa and New Hampshire. Earlier this month he spoke to the Conservative Political Action Conference, a crucial stop for GOP presidential contenders.
But the nuts and bolts of a campaign never seemed to coalesce. During a meeting with New Hampshire activists, he defended specific spending requests, known as earmarks, he secured for his state. Earlier this year, he shook up his fundraising team.
Aides sought to downplay the significance of the move while cautioning that Thune had yet to decide whether to seek the nomination.
With six years each in the U.S. House and Senate, Thune has spent considerably more time in Congress than Obama had when he was elected president. His opposition to gay marriage and abortion has earned him points with evangelicals, while his pro-business, anti-tax and pro gun-rights stances have garnered support among more libertarian leaning conservatives.
But some have criticized Thune's vote for the Wall Street bailout in 2008. Thune acknowledged that vote was "clearly an issue for a lot of conservatives."
With Thune's exit, it appears the most serious White House contenders will be current and former governors who will campaign on their records running statehouses.
Asked if his decision not to run next year was final, Thune demurred.
"I don't think you ever totally rule things out, but I wanted to come to closure on this," he said. "For me, for now, my work is in the United States Senate."
Elliot reported from Washington. Associated Press writer Charles Babington also contributed to this report from Washington.