<br /> Politico reports that the Senate battleground map has shrunk dramatically in recent weeks. It's a net plus for Democrats. But it might not be enough to change their status as heavy underdogs to win the chamber in November.<br />Democratic incumbents look increasingly safe in four Rust Belt states President Trump carried in 2016 — Ohio, Michigan, Pennsylvania and Wisconsin. There Republicans are locked in a bitter primary until August. Both parties agree a core universe of states are truly in play. <br />
