This week, Rep. Ron Paul (R-Texas) took a significant step toward launching another bid for the GOP presidential nomination, announcing that he is forming a campaign exploratory committee — a key fundraising vehicle that typically precedes the official launch of a campaign. Paul, who is popular with libertarians and Tea Party activists, said his candidacy would be "a reflection of a grassroots movement." But he finished fifth in the crucial Iowa caucuses in 2008, and he's considered a longshot in 2012. So why is he running? Here, five theories:

1. He wants a platform for his libertarian views
Paul's "third ride on the presidential merry-go-round" probably won't be any more successful than his unsuccessful bids in 1988 and 2008, says Linda Feldmann in The Christian Science Monitor. But he's not out to win the White House; he's simply seeking TV exposure for his limited-government views, and face time in high-profile debates.

2. Paul can influence the party's pick
"Ron Paul's not as big of a joke as people think," says Tom Jensen at Public Policy Polling. He may not have a serious chance at winning the GOP nomination, but "he will pick up a lot more support than many of the other folks sucking up the media air." His favorability numbers in Iowa are better than everyone but Mike Huckabee's, and he polls well in New Hampshire, too. "With a weak field that the Republican base is unenthused about, I bet he'll be a much bigger player this time around than he was in 2008."

3. If nothing else, he'll keep the others honest
Paul will open up the debate on foreign policy, says Andrew Sullivan at The Daily Beast, and he'll continue pushing the GOP away from "big government conservatism to a more Paulite view of the role of the state." Most importantly, he'll offer an alternative to Palin, Gingrich, Trump, and Romney — all of whom are "obvious liars, positioners and, to a greater or lesser extent, frauds." Whatever you think of Paul's views, the man has integrity, and that should count for something.

4. He'll harness Tea Party energy
Paul "is less a leader than a symbol," says Michael Scherer at TIME, "the eye of an ever-widening hurricane of libertarian discontent that has seized the imagination of young people, fiscal conservatives and others across the county." In 2008, "his supporters' ebullience" caught him by surprise, and he didn't collect enough delegates to win the right to speak at the GOP convention. But this time around, he's starting out with solid poll numbers and confidence in his ability to raise piles of campaign cash. That should make him and his Tea Party backers more of a force within, and for, the Republican Party.

5. And he could actually win
The conventional wisdom is that Paul stands no legitimate chance, says Drew Ivers, a member of the state central committee of Iowa's Republican Party and a Paul supporter, as quoted by The New York Times. But 2012 could be different. Paul is "in the epicenter of the three or four or five the most critical and controversial issues in our nation today," including government spending, the war, and the financial crisis. "That's how snowballs develop, you know. They start small, and they get bigger as they roll downhill."