From the Capital Tonight morning memo, the first item:

Former Gov. George Pataki this morning endorsed Republican Westchester County Executive Rob Astorino for a second term.

The advisory for the Pataki endorsement was emailed out yesterday afternoon, which a handful of reporters dutifully tweeted, but otherwise left alone.

Barry Caro, a spokesman for Astorino’s Democratic challenger, New Rochelle Mayor Noam Bramson, didn’t leave it alone. He took issue with the Astorino campaign playing up its strength “environmental issues” with the Pataki endorsement and began a barrage of tweets at this mild mannered reporter blasting the CE’s record on the environment.

A reality check: Pataki’s endorsement is not a game-changer in the Westchester County executive’s race. Yes, he’s a Republican former governor who was elected three times in deep Blue New York and still has ties to Westchester County where he is from.

But a Republican endorsing a Republican is barely above man bites dog.

Still, the episode speaks to a larger issue about the race for Westchester county executive: It is likely at this point going to be extraordinarily close and is already very heated.

Astorino was elected in 2009, winning an upset victory over three-term incumbent Andrew Spano.

It was all the more unusual that the telegenic Republican was elected in a suburban county that had been trending increasingly Democratic.

Statewide, Republicans rejoiced: Finally here was someone they could legitimately claim was a rising star with potential statewide appeal.

Democrats, however, really want this seat back.

The suburbs of New York City, especially along the lower Hudson Valley corridor are an important swing region of the state.

Yes, it’s increasingly Democratic and multicultural. But Westchester residents also live under one of the highest property tax burdens in the country. Astorino rode a wave of anger over increasing county spending and taxes (and most likely fatigue of three terms of the same guy).

In other words, Westchester’s political mindset informs why Gov. Andrew Cuomo (himself a county resident) has had success for being a fiscal moderate and social liberal.

That’s why a Republican who can manage getting elected there is automatically considered a statewide candidate (Astorino of course denies he’s interested in running for governor). For historical purposes, Gov. Mario Cuomo’s 1986 opponent was Westchester County Executive Andy O’Rourke, who was completely and utterly trounced in that election.

Democrats earlier this year in the county convened and decided they weren’t going to commit to the usual fratricide of a primary.

A convention produced a nominee: Bramson, a handsome, energetic mayor of a small-ish urban area who is a protege of longtime Rep. Nita Lowey.

Almost immediately, the volleys between the Astorino and Bramson camps began.

Bramson is accused of giving himself a pay raise! New Rochelle is taxed too much! The county executive disagrees with the SAFE Act! Astorino was endorsed by a “sham” organization! The horrors!

Pity the voters in Westchester who have to wade through this stuff for the next five weeks.

Needless to say, the stakes are high in this race.

A Republican loss would all but remove one of the last potential GOP bench players (save for former U.S. Attorney Michael Garcia and Marc Molinaro, the Dutchess county executive) and be a devastating psychological blow to Republicans.

An Astorino win wouldn’t necessarily have a statewide punch other than provide a potential road map for other Republicans in Democratic areas for how to win (Astorino has been aggressively courting black community leaders in cities like Mount Vernon).

Keep an eye on Westchester.