President Obama’s behavior over the past year, and particularly the last month, borders on bizarre. The candidate who promised to bring people together and move beyond polarization has morphed into a divisive and defensive president.

His sinking approval numbers underscore the growing public disappointment in the gap between his campaign rhetoric and his governing style.

The president’s thin skin at news conferences is now part of Washington press corps lore. His “ass kicking” comments about the Gulf oil spill were weird and un-presidential. Lately, he’s resorted to criticizing individual members of Congress personally at town hall events, tactics more suited to a rookie political hack than the leader of the free world.

What happened?

Some believe the president is just stressed out.  Maybe he could use a few beers and a couple smokes with his buddy Joe Biden in the Rose Garden. After all, to paraphrase the vice president’s comments about health care: This job is a big [expletive] deal!

But the president’s madness may also have a method. He needs to avoid electoral disaster in November.  These off year contests are different -- more about turning out base voters than persuading the less committed.

Obama’s peculiar tactics are intended to do just that.  Fire up the faithful now; worry about swing voters in 2012.

How?  First, instead of seeking bipartisan legislative consensus, he uses his party’s majority power like a steamroller.  Democratic partisans swoon when Speaker Nancy Pelosi crushes Republicans using the House’s unique majority procedural powers.

Next, every Obama initiative also includes a designated villain.  Turning political opponents into piñatas always riles up the base. Democrats built momentum for passing stimulus legislation last year because of the mess President Bush left behind. When toutin health care, they blasted greedy insurance companies. And, of course, the Wall Street reform emasculated the big banks before they could spend any more of those obscene CEO bonuses.

Taken together, these tactics are an attempt to energize partisan Democrats prior to November.  And Obama needs their help. A quick look at midterm turnout patterns explains why the president has cause for alarm.

The electorate always looks different in non-presidential years.  For example, just over 80 million Americans voted, or about 37 percent of the voting age population (VAP) in 2006.  But two years earlier in the 2004 presidential contest, 122 million showed up on Election Day (over 56 percent of the VAP).  In other words, over 41 million fewer votes were cast in 2006 compared to 2004.

This was no fluke. Looking back at recent midterm elections, turnout usually drops about 20 percent from the presidential election two years prior.

About 132 million people voted in 2008.  Based on history, thirty to forty million of them won’t show up this November.

Who are the higher and lower propensity voters?  History again provides some insights here. Age is one key variable. Midterm contests include a higher percentage of older compared to younger voters.

For example, in 2008, Americans 65 and older represented about 16 percent of the electorate, while 18-29 year olds made up a slightly larger 18 percent of the total, according to exit polls. In 2006, however, older voters represented 19 percent of the total compared with only 12 percent for the younger bloc.

How are these older and younger voters stacking up to the last midterm election in 2006?  Pew Research released a poll last week demonstrating a massive GOP turnaround with older voters compared to four years ago.

Democrats held a 14-point lead with voters over 50 in June of 2006. Today, the GOP enjoys an 11-point lead with this demographic – a net 25-point swing among these high propensity midterm voters.

Turnout rates are also higher among those who say they are more enthusiastic or following the election closely. Here again Pew finds a massive shift compared to four years ago. In June of 2006 Democrats led Republicans by 16-points on vote enthusiasm.  Today, the GOP enjoys a 14-point edge.

The president’s name is not on the ballot this November.  Still, the midterm election will significantly impact the White House, shaping the final contours of his first term.  Losing the congressional majority translates to a major political setback.

Some might think Obama needs anger management. After all, vilifying businesses and kicking some Republican butts around the country seems more fitting for an irate community organizer than a transformational political figure.

Yet the president’s actions are very sane.  Put transformation on hold and get the base “fired up and ready to go.” Failure to do so will produce another political butt kicking: his own.