Smooth, rocky or in between, relationships between the leader in the White House and the House speaker on Capitol Hill can be the most important and defining in a presidency. Donald Trump and Paul Ryan were hardly pals during the campaign, but they appear to be moving together now.

Here are some of the significant president-speaker pairings in recent years:

—Republican President Ronald Reagan and Democratic Speaker Thomas “Tip” O’Neill. The conventional wisdom holds that this pair of Irish-American politicians would fight like partisans during the day only to savor their friendship with a post-6 p.m. drink, but in reality their relationship was often contentious. Reagan rolled over O’Neill in 1981 to win his first signature accomplishment — tax cuts — but a 1983 overhaul of Social Security and the much-lauded 1986 tax reform measure were products of difficult, but ultimately successful, negotiations.

—Democratic President Bill Clinton and Republican Speaker Newt Gingrich. Republicans broke a four-decade hammerlock on Democratic control of the House in 1994 by running against Clinton’s agenda on taxes and gun control, but an over-reaching Gingrich was Clinton’s foil two years later as the Democrat easily won a second term. They brokered a 1997 budget pact, but perhaps their defining episode was the 1998 Monica Lewinsky scandal and impeachment drive — which tarred Clinton’s legacy and ended Gingrich’s speakership after it led to surprising midterm losses for Republicans.

—Republican President George W. Bush and Republican Speaker Dennis Hastert. Bush won the 2000 presidential race only narrowly and Hastert commanded a slender House majority. But with the help of a handful of Senate Democrats, Bush and Hastert powered home an agenda of tax cuts, battled terrorism and expanded Medicare. Hastert later was convicted on a bank fraud case linked to cover-up allegations regarding sexual abuse of teen boys.

—Democratic President Barack Obama and Democratic Speaker Nancy Pelosi. Obama may have been chairman of the board, but Pelosi acted like a chief executive officer during his first two years in the White House, engineering most of Obama’s congressional accomplishments and running the Democratic-controlled House with a whip hand. She was a principle architect of the Affordable Care Act, but her hard-fought legislation to combat global warming stalled in the Senate.

—Obama and Republican Speaker John Boehner. The Ohio Republican was swept into the Speaker’s post in the 2010 midterm landslide, but often displayed only tenuous control over his caucus of tea partyers, who were suspicious of his dealings with Obama. Boehner failed on two occasions to win a major budget pact with Obama, though a 2011 budget and debt agreement ended up cutting agency budgets. Boehner was pushed out last year amid continuing struggles on his right flank.

(AP)