Running for president is a grueling, full-time job that consumes your life, your privacy, your personal space, and, often, your bank accounts. And in the end, only one candidate from each party advances. Essentially, "your life is officially on hold for a year and a half, or longer if you happen to be 'lucky enough' to win" the nomination, says Doug Mataconis at Outside the Beltway. But most candidates have little or no shot to get even that far. Why would "any sane person" choose to stage a thankless, longshot bid for the White House? Here, five theories:

1. It can be lucrative
Some long-shot candidates literally treat running for office as a full-time job, says Todd Jacobs at Yahoo! News. Newt Gingrich, and maybe-candidate Sarah Palin, are basically using their free media appearances and campaign contributions to stage profitable book tours. It is past time for Newt, especially, to "sell books on his own dime and quit wasting Republican donor money." And "why is Herman Cain running?" asks Ron Elving at NPR. Since he can't win, it sure looks like he hopes to "enhance the marketability of his motivational speaking and talk show career."

2. It's supposedly part of God's plan
Some 2012 aspirants feel they are called to run — literally. Rep. Michele Bachmann's (R-Minn.) star is rising in the GOP, but she says that she's listening to God more than pollsters. On CBS's Face the Nation on Sunday, Bachmann reiterated that before making political decisions, she prays, and that her prayers have provided her with a "sense from God" of "assurance about the direction" her political career is taking. "That's what a calling is," she added.

3. It raises your profile for future success
For several of the Republicans running for president this year, the goal isn't really to become president in 2012. "It takes imagination to discern a path to the nomination for [Jon] Huntsman," for example, says NPR's Elving. He's probably betting his elevated profile during this cycle will help him in 2016. Other candidates, like Rick Santorum and libertarian Gary Johnson, are probably "auditioning for a job in a future Republican administration," and Tim Pawlenty is looking "very vice-presidential" in his soft-footing around frontrunner Mitt Romney.

4. It raises the profile of your pet cause
Some candidates enter the race to make sure the issues they care about are part of the Republican conversation — like Gary Johnson and drug legalization, or possible entrant Rep. Thaddeus McCotter (Mich.) and his more literal pet issue, a bill that would "allow pet owners a $3,500 annual tax deduction for 'qualified pet-care expenses.'" The king of running to make a point is libertarian "gadfly" Rep. Ron Paul (Texas). This time around, during his third run at the White House, Paul's views on abolishing the Federal Reserve, re-adopting the gold standard, and instituting a non-interventionst foreign policy are being taken seriously, says Catherine Dodge at Bloomberg, and his rivals no longer "laugh or snicker" when he speaks.

5. It's the manifestation of a candidate's hubris (or delusion)
For those dark horse candidates who think they will actually prevail, no small amount of delusional self-confidence is involved. If you look up hubris in the dictionary, it's hard not to see Gingrich's face, says Jules Witcover in the St. Augustine Record. And so far, his "know-it-all pomposity and inflated sense of his own superiority" hasn't served him well. But hey, Newt's "terminal hubris" may be no more disqualifying than the "fatal mistakes and irreparable flaws" that characterize the other candidates who think they can win the nomination, says Steve Chapman at Reason.