Trump is still playing on his home turf

Republican presidential candidate Donald Trump supporter Chanell Temple yells at anti-Trump protesters during a rally in front of the Anaheim City Hall in Anaheim, California. Photo / AP

Exit polls are very useful for telling us specifics about who came out to vote, which candidates they supported and why.

Today, though, we don't really need them.

Donald Trump was quickly declared the victor in the biggest primaries in Connecticut, Maryland and Pennsylvania because, a week after dominating in New York, he's still playing on his home turf.

Trump has won every state touching any of the states that voted today, save Ohio.

Rhode Island and Connecticut are hemmed in by New York and Massachusetts, which Trump won by 35 and 31 points, respectively. Maryland and Delaware are closer to Virginia, which Trump won by a narrower margin - but that was back on (the original) Super Tuesday, when Marco Rubio was around to chew up 32 per cent of the vote.

Geographically, this is Trump territory. If you wanted to drive from Trump Tower to any point in the five states, the most it would take you is about six hours (assuming you got out of Manhattan quickly).

This is an area that's light on the sort of hard-right conservatives and evangelicals among whom Ted Cruz has been more competitive. On average, 56 per cent of Republicans in states for which we have exit poll data so far have identified themselves as evangelicals and 34 per cent have identified themselves as "very conservative".

We have preliminary exit polls from Pennsylvania, Maryland and Connecticut, reported by CNN. In Pennsylvania, about half of the voters were evangelical and 3-in-10 were very conservative. In Maryland, fewer were evangelical. In Connecticut, only about a quarter were very conservative and a fifth evangelical. Not that it mattered; Trump won all of those groups anyway.

In Pennsylvania, in fact, nearly six in 10 evangelicals voted for Trump. In past contests (many with more candidates), Trump has averaged 36 per cent.

Over the course of the campaign, Trump's strength has come from a hardcore group of support that makes up its mind early and sticks with him.

There's a loose correlation between how much of the electorate made up its mind early and how well Trump does. Today, it happened again. Six in 10 voters in Maryland made up their minds before a month ago, and six in 10 of them went for Trump. The same percentage made up their minds early in Pennsylvania, but went even more heavily for Trump. Same in Connecticut.

Which suggests that in places where Trump's got natural strength, the "stop Trump" effort doesn't count for much. People made up their minds a long time ago and stuck with their guy. Among those that made up their minds in the last week, John Kasich triumphed in Connecticut and ran close in Maryland. But that wasn't many voters.

We spend a lot of time trying to figure out what's genuine traction and what isn't, which of these contests suggest that something has changed and which don't.

Wisconsin, which Cruz won conclusively, lined up neatly with the start of the stop-Trump push. But Wisconsin isn't the Northeast. Trump lost Minnesota and Iowa, Wisconsin's neighbours to the west. It's a place where Trump may have been expected to do worse. It seems clear that those results didn't do much to turn heads in New York or elsewhere in the Northeast.

That also means that Trump's winning streak may stop cold. The states east of the Mississippi have been very good to Donald Trump, but most of what remains is to the west.

He'll get a lot of delegates today, which he needed to.

But this was a big win with home-field advantage against a wobbly opponent.

His ability to hit the 1237 delegates he needs in order to clinch the nomination is still uncertain.

After today, that only gets harder. But then, it's hard to see how it could get much easier.