Rick Santorum hasn't won any big swing states -- and he's in danger in his home state Pennsylvania -- and doesn't have much of a shot at catching up with Mitt Romney, so the headlines declaring the end of the Republican primary are beginning to cascade. Since the race has seemed to be essentially over a couple times, it's a little scary to declare it's over. But on Thursday, several people had the courage:

  • "Romney edges into mop-up phase of campaign," The Associated Press' Matt Espo
  • "In GOP Presidential Race, Fat Lady Finally Sings," Roll Call's Stuart Rothenberg
  • "The Beginning Of The End," ABC News' Michael Falcone

Those follow similar headlines from earlier this week:

  • "Republican Race `All But Over,' Ex-Rep. Davis Says," the Washington Post, March 26
  • "The 'walking dead' phase of the Republican primary is upon us," The Washington Post's Chris Cillizza, March 26.
  • "Poll Shows Even Republican Voters Know The Race Is Now Over," Business Insider, March 28

Still, there were some holdouts Thursday.

  • "Rick Santorum’s ‘Win or go home’ states," The Washington Post's Aaron Blake
  • "Santorum's last chance (really, this is it)," NBC News' First Read.

The New York Times' Nate Silver lays out the cold cruel math that this last shot is a long one. While Wisconsin's "idiosyncrasies" make it a little more favorable to Santorum than demographics would suggest, "with Mr. Romney having the advertising advantage in Wisconsin, as he usually does, Mr. Santorum is more likely to achieve an upset there by changing the national conversation than by grinding out a victory tooth-and-nail." He also can't count on getting Newt Gingrich's voters. Expect even more "Goodbye, primary" headlines next week.