Candidates looking to take down sitting members of Congress in primaries are stockpiling cash as their races heat up, according to fundraising reports filed Wednesday — and it’s Democratic lawmakers who are mostly on defense. At least nine House Democrats and one Democratic senator, Ed Markey of Massachusetts, were outraised by their primary challengers in the first fundraising quarter of the year, suggesting the energy within the party that is clamoring for new leaders is fueling some of these