It has been nearly a year since Barack Obama was sworn in as the 44th president of the United States. So what can his first year in office tell us about the next three?

Everything, most armchair historians say. The first year of a presidency is a make-or-break opportunity for an administration to assert control of Congress, achieve its legislative priorities and impress the American people with its effectiveness.

Many of Obama’s supporters also buy into this idea. They can be heard comparing the president’s first year in office to that of Franklin D. Roosevelt, and otherwise describing the year’s achievements in effusive terms. Meanwhile, the president’s critics compare his job approval numbers, which have steadily dipped during this first year, to those of past presidents. They say these numbers show that the more people get to know Obama, the less they like him — and the less they will like him in the years come.

But a closer look at history suggests that both too much and too little can be made of a president’s first year in office.

1. Congress is your willing handmaiden.

In the afterglow of the 2008 elections, when the country had not only overwhelmingly elected Obama president but had also handed Democrats wide majorities in the House and Senate, many in the Democratic Party had the sense that after years of frustration, a progressive agenda would finally be enacted.

Or not. While Congress has passed several of Obama’s agenda items — the expansion of the Children’s Health Insurance Program; the Lilly Ledbetter Fair Pay Act, which makes it easier for women and others to sue for wage discrimination; the economic stimulus package — it has been more of a roadblock than a thoroughfare on other priorities, including health care reform.

The past two U.S. presidents also found that having their party in control of Congress didn’t guarantee anything: Bill Clinton couldn’t get health care reform through a Democratic-led Congress in 1993 and George W. Bush’s efforts at reforming Social Security following his 2004 reelection failed miserably, despite Republicans in charge of Congress.

Recent history provides cautionary tales for lawmakers who might be inclined to rubber-stamp a new president’s agenda. According the American Presidency Project at the University of California at Santa Barbara, the Democratic-controlled House and Senate voted in lockstep with Clinton 86.3 percent of the time in 1993 and 86.4 percent of the time in 1994 — setting the stage for Republicans to take over Congress in that year’s midterm elections. In 2004, congressional Republicans voted with Bush 81 percent of the time, then lost 30 House seats to Democrats.

1. Nothing gets done legislatively after the first year.

Most presidents consider their first year in office their best chance to enact their most ambitious legislative priorities. It’s far enough ahead of the midterm elections to get nervous members of Congress on board and three years before the next presidential election — so they’ll have time to reposition themselves if support for their agenda goes south.

The problem with treating the first year as a be-all and end-all? It ain’t necessarily so. Ronald Reagan overhauled the country’s tax code six years into his presidency, and Bush signed a bill regulating the accounting industry, the Sarbanes-Oxley Act, in summer 2002.

1. Your party’s base abandons you.

The bases of the two parties don’t understand or care much about the sausage-making aspects of how policy is constructed in Washington. They want action, and they want it now.

And so when Obama didn’t manage to bring all U.S. troops home from Iraq, reform the health care system and abandon the “don’t ask, don’t tell” policy for gays in the military (among other things) in his first week in office, there was consternation within the Democratic base.

But that consternation rarely turns into large-scale abandonment. President Jimmy Carter was widely disliked among the party’s base following his 1976 victory, so much so that Sen. Ted Kennedy challenged him in 1980. Carter still won. Clinton’s “Third Way” centrism didn’t sit well with the party’s base, but he still was re-elected in 1996.

1. The first 100 days don’t really matter.

The first 100 days do matter, and for one simple reason: You never get a second chance to make a first impression.

Famously influential first 100 days like those of Roosevelt, who used his initial months in office to grow government to try to pull the country out of the Great Depression, and Reagan, whose first 100 days were dominated by an effort to undo many of the government-growing policies put in place five decades before by Roosevelt, were marked by intense activity, broad change and wide-ranging political consequences.

The Obama presidency began with a flurry of accomplishments — passage of a $787 billion economic stimulus package, approval of his $3.6 trillion budget and the allocation of money from the Troubled Asset Relief Program to bail out the nation’s banks — that shaped everything that came after.

But the first 100 days can also matter in ways no one anticipates: Although Obama seemed to defy political gravity in his first few months, the actions he took during that period led to a rallying of the Republican base and eroding support among independents.

1. After the high of winning the election, your approval ratings have nowhere to go but down.

Most presidents arrive in office with approval ratings in the 60s, as the American public — an optimistic bunch — proves itself willing to give the newly elected leader the benefit of the doubt.

Where the numbers go from there depends on what the president does. Bush, who came into office on the shakiest of electoral grounds, pursued a decidedly conservative agenda on the home front and a go-it-alone approach to foreign policy that (understatement alert!) didn’t sit well with the American people. Except for an extended bounce after the Sept. 11, 2001, attacks, his public support steadily declined over the years.

Clinton, on the other hand, encountered some ups and downs at the start of his presidency, but because of centrist policies and a thriving economy, he managed to end his presidency with two-thirds of the country approving of the job he had done.

Reagan followed an arc similar to Clinton’s. He took office with the lowest approval rating (51 percent) of any U.S. president in the modern era. Eight years later, because of a popular foreign policy, tax cuts and a sunny leadership style, he left office with a sky-high approval rating second only to Clinton’s among post-World War II presidents.