Given that old adage, “You can’t tell where you’re going unless you know where you’ve been,” casting a close eye over last year’s congressional voting patterns is in order.

Sure, that was an election year for a divided Capitol, while Republicans now run the whole show and their performance isn’t subject to formal assessment by the voters until next year. But still, members behaved in the second half of the 113th Congress in ways distinctive enough to create several storylines to watch throughout the 114th.

Some of the best evidence for that comes from the vote studies conducted annually by CQ Roll Call since the early 1950s. They provide empirical assessments of the previous year’s congressional partisanship and presidential support — both in the House and Senate as institutions and in the ballots cast by each lawmaker. (You can peruse or download all the numbers for the previous year at CQ.com.) Comparing the results year over year and as six-decade trend lines offers proof positive that partisanship and polarization are the drivers of legislative behavior more than in any other period since at least the start of the Eisenhower administration.

Having had that unmistakable impression reinforced, here are four other takeaways from the 2014 studies that are useful to remember in 2015. There is one for each caucus:

About the House Republicans: Speaker John A. Boehner has been having an easier time, or at least easier than it’s appeared during so many internal caucus standoffs, unifying his factions of establishment conservatives and ultra-confrontational conservatives.

Last year, the Republican Conference mustered unprecedented resistance to a president’s agenda: Barack Obama prevailed on only 15 percent of the House roll calls where his position was well understood in advance, the lowest success rate in the 61 years we’ve been taking such measurements. And, as in the previous three years since taking back the majority, GOP members strayed from the partisan line less than 10 percent of the time — a record for sustained party discipline unmatched in the House in the history of our party unity studies.

Especially noteworthy is that on the roster of 12 Republicans who went against the grain, more than an eighth was comprised entirely of centrists; not a single member of the tea-party-infused “Hell No” caucus made the list of top iconoclasts.

About the House Democrats: There’s a simple reason the ranks of centrists on this side of the aisle is shrinking close to oblivion, and only a few years after the species “Republican moderate” got similarly downgraded from endangered to statistically extinct. Democrats who trend conservative are not able hold onto their jobs — even in swing districts.

Last year, 13 lawmakers topped the roster of Democrats who opposed Obama most often (at least two-fifths of the time) as well as the list of those who most frequently strayed from the rest of the caucus (at least one-fifth of the time). Five were defeated last November, while three retired rather than wage uphill fights in purple or red territories. Three survived in districts Obama carried in 2012: Henry Cuellar of Texas, Kyrsten Sinema of Arizona and Jim Costa of California. But only two of the most against-the-grain Democrats were re-elected from districts Mitt Romney carried: Collin C. Peterson of Minnesota and Patrick Murphy of Florida. (They’ve got company from Arizona’s Ann Kirkpatrick, who was more of a party loyalist, and a pair of freshmen who won upsets in Romney territory: Gwen Graham of Florida and Brad Ashford of Nebraska.)

About the Senate Democrats: Harry Reid created some unintended and not all that helpful consequences for the caucus with both his big strategic objectives during what may have been his final year as majority leader: Preventing roll calls that would have been politically problematic for his side, and maximizing confirmations in the new “post-nuclear” world where nominations can’t be filibustered.

Reid got what he was after on both fronts. Senators cast just 20 votes during the entire election year on legislation the president cared about, but they held a record 125 votes on his nominees for judgeships and executive branch positions. That allowed for some skewed perceptions. Obama himself may be surprised to learn he got his way in the Senate 93 percent of the time, given that almost none of his policy agenda advanced there. More problematically for the Democrats is that virtually all of them came across as way more supportive of the president than is in their best interests, or accurately reflects their ideologies. All five who were defeated last fall — each after campaigning as an “independent voice” more attentive to constituent concerns than presidential appeals — backed Obama at least 96 percent of the time.

Will Colorado voters care that Michael Bennet, for now the only Democratic senator besides Reid vulnerable to defeat in 2016, entered his re-election cycle backing Obama 99 percent of the time?

About the Senate Republicans: What Reid did made this group’s behavior look pretty squirrely, as well, and the new Majority Leader Mitch McConnell has an opening to put them back on a more predictable path.

With so few opportunities to go on record opposing Obama’s policies, and so many relatively non-controversial nominations on the docket, GOP senators had relatively few opportunities in 2014 to put their disdain for the president’s ideas on the record. With that antipathy bottled up, the CQ Roll Call Senate Republican presidential support score ended up at 55 percent — remarkably, the highest for that caucus during a Democratic presidency except for 1997, a year of actual deal-making between Bill Clinton and a GOP Congress.

The four readying 2016 presidential runs supported Obama more than half the time. And so did every GOP senator expecting a tough fight for re-election next year. In fact, Reid may have done the other side a small backhanded favor, creating a situation that allows Republicans running in states Obama carried in both his elections to say they’ve bent over backwards to back him when they can. Mark S. Kirk of Illinois (66 percent), Kelly Ayotte of New Hampshire (64 percent) and Rob Portman of Ohio (63 percent) all made the top 10 leading presidential supporters within their conference.

Those numbers help explain why the average Senate Republican party unity score last year was 84 percent, even as the averages topped 90 percent for the other three congressional camps. For seven of McConnell’s eight years as minority leader, in fact, his team’s collective party unity was the lowest of the four caucuses. Being promoted to the top job gives him a decent opportunity to alter that.

Related:

See the Full Vote Study at CQ.com

Vote Studies Show Double-Sided Numbers for Senate’s ‘Red State Four’

The 114th: CQ Roll Call’s Guide to the New Congress

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