President Obama’s second term starts today. It ends sooner than you think.

President Obama's second term begins today and ends in four years time. Except that in political terms, it will be over far sooner than that.

President Obama was sworn in for a second term on Sunday.

The reality is that a clock started counting down the minute Obama took the oath of office on Sunday, a clock that will likely run out of time in, roughly, July 2014. As White House communications director Dan Pfeiffer told the Post's Scott Wilson: “Days in your second term are in many ways more important than in your first."

Here's why.

At the moment, President Obama is at the height of his political influence. He is less than three months removed from a convincing reelection victory and freed from concerns about ever having to run for office again. He is coming off of two straight legislative wins -- fiscal cliff and debt ceiling -- and has a huge polling edge over his congressional Republican adversaries.

That means that now is the time for Obama to move on his major legislative priorities -- the first of which appears to be winning some sort of tightening of existing gun laws in the wake of the Newtown, Conn., tragedy. Obama also seems likely to push  on immigration. And then there is the triple-headed economic monster: sequestration, a potential government shutdown and the debt ceiling.

The president must choose carefully how hard he pushes on each of his priorities -- and for how long. Much of his first term -- and the political capital he brought into it -- was spent on fights over the economic stimulus package and his health-care plan.  While both of those legislative initiatives became law, it was at considerable political cost to Obama and his party -- and at the expense of other priorities like energy, for example.

No matter what pieces of the Obama agenda mentioned above make it through Congress as spring turns to summer in 2014, the attention of the political world will turn away from legislative fights and to the coming midterm campaign. (Prepare to hear a lot about the so-called "six-year itch" election.) In expectation of that election, Congress will avoid any sort of major legislative action from the summer on as both parties seek to avoid exposure as they make their case to voters in the fall.

Once the midterms end, the 2016 presidential race, which is already showing signs of getting started, will burst out into the open with a few candidates likely declaring their intent to run by the close of 2014. With the race expected to be open on both sides -- assuming Vice President Biden decides not to run -- the level of interest in the contest to come will be substantial. (Human nature dictates that we love the next big thing more than the current big thing.)

Add it all up and what you get is this: By the start of 2015, Obama's power to drive his legislative agenda will be significantly less than it is today. What his second term meant (or didn't) will have already be largely determined by then.

The president has 18 months, then -- give or take a few months -- to build out his political legacy. Which means he needs to get moving as quickly as possible or run the risk of running out of political power before he can get done even most of what he hopes will round out his presidency in this second term.

Fixbits:

Obama was officially sworn in to his second term Sunday, though all the inaugural festivities will be held Monday.

Senior Obama adviser Valerie Jarrett says Obama's cabinet, "when he's finished -- and he's far from finished -- will have diversity, including women, including people of color."

Sen. Charles E. Schumer (D-N.Y.) says the Senate will pass a budget this year, after failing to do so in recent years. And that budget is likely to include tax increases.

Sen. Ted Cruz (R-Tex.) says the so-called "gun show loophole" doesn't exist.

Sen. John Barrasso (R-Wyo.) doesn't even think Senate Majority Leader Harry M. Reid (D-Nev.) will bring Obama's gun proposals up for a vote.

Ashley Judd says she's still hedging on whether or not to run for Senate in Kentucky.

A Democrat in the Nevada state assembly is in jail after threatening the assembly's speaker-elect with a loaded gun.

Mo Rocca looks at the hastiest inaugurations in American history.

Must-reads:

"Obama’s oratory: A gifted speaker has unfinished business for inaugural address" -- Joel Achenbach, The Washington Post

"A new term, but old divisions" -- Dan Balz, The Washington Post

"For Second-Term Presidents, a Shorter Honeymoon" -- Nate Silver, the New York Times

"A new term, a new Obama" -- David Maraniss, The Washington Post

"Obama's Ethics Agenda Backfires" -- Eliza Newlin Carney, Roll Call

"Mass-shooting survivors making push for gun control their lifes’ work" -- Brady Dennis, The Washington Post

"Four Years Later, Checking In With Those He Sought to Help" -- Jada F. Smith, the New York Times

"A more confident Obama emerges for second term" -- Domenico Montenaro, NBC News

Also on The Fix

Chuck Schumer: Senate will pass a budget