Senate races are not House races.

This seems obvious. But amid increasing chatter about just how bad the national environment will be for Democrats in midterm elections this fall, it’s an important point to remember.

House races, in this modern political age, are almost entirely dictated by the national landscape. It’s virtually impossible for any House candidate to stand out (or above) the national environment. Senate races — featuring better-known candidates and lots more money — can buck national trends (although they don’t always). Senate races have become, in effect, mini presidential races and, like presidentials, can create their own gravitational pull.

“The recent generic ballot numbers showing the GOP ahead add very little to the debate over whether Republicans will take over the Senate,” said Neil Newhouse, a prominent Republican pollster and partner at Public Opinion Strategies. “No one, repeat, no one on our side is measuring the drapes for GOP control of the Senate. Campaigns matter, and this one has only just begun.”

Let’s dig into those generic ballot numbers Newhouse mentioned. Many Republicans — though not Newhouse — were over the moon when new Pew Research Center polling showed Republicans with a 4-percentage-point edge when voters were asked which party they would like to see control Congress after the November elections. (A CNN survey released shortly after showed Republicans with a 1-point edge on the generic ballot question.)

The Pew numbers compare very favorably to where things stood at this time in 2010 — Democrats had a 10-point edge in the generic then — just months before Republicans took back the House by picking up 63 seats.

That is, without doubt, very good news for Republicans hoping to maintain or perhaps even increase their 17-seat majority in the House. But, in truth, no one but the biggest Democratic homers thought that the House was in play in this election. Between a Republican-dominated redraw of congressional lines in 2010 and the weight of history (the president’s party has lost an average of 29 House seats in second-term midterms since World War II), the high likelihood — even before the national environment started to tip toward Republicans — was that Democrats would remain in the House minority.

The tendency in political circles is to extrapolate those House projections onto the Senate playing field. And, there is little doubt that people like Mary Landrieu in Louisiana, Mark Pryor in Arkansas and Kay Hagan in North Carolina would rather be running in a national environment that looks more like 2008 than the one they are likely to have to deal with this year.

But, assuming that simply because Republicans are poised to easily hold the House this fall means they also have in the bag the six seats needed to retake the Senate suggests a lack of understanding of how different the races for the two chambers are.

First, races for Senate traditionally feature more established and better-known candidates. Typically, the nominees for Senate are elected officials — at the state or federal level — and have run and been elected statewide previously. This gives them a base of name recognition and support that people running for the House — up to and including incumbents — typically do not enjoy. That makes it harder — though far from impossible — to savage a Senate nominee as a tool of an unpopular national party.

Second, Senate races attract so much more money than House races. The most expensive Senate race in 2012, according to calculations made by CQ Roll Call, was the Massachusetts contest between Elizabeth Warren (D) and Scott Brown (R), which had a $85 million price tag. The most expensive House race was in Florida’s 22nd District, where $29 million was spent. The spending — by candidates as well as outside groups — means that voters in Senate races almost always are making a candidate-based decision rather than a party-based one.

North Dakota in 2012 is indicative of these differences. Republican presidential nominee Mitt Romney won the state by nearly 20 points, and Kevin Cramer, the Republican, cruised to a win in the state’s open House seat. Yet, Heidi Heitkamp (D) managed to win the state’s open Senate seat over then-Rep. Rick Berg (R).

To be clear: You’d still rather be Senate Republicans than Senate Democrats right now. Although the national environment will be far less decisive in Senate races than in House contests, it is still likely to matter at the margins — and often those margins are where close contests are decided. And the states in which the Senate majority will be decided — including Alaska, Arkansas and Louisiana — lean heavily toward Republicans.

But national environment isn’t entirely decisive in modern Senate races. Candidates and the campaigns they run matter, too. And that’s why Democrats still have some hope of holding on to the Senate in November.