Roughly half of House and Senate Democrats skipped President Trump's State of the Union address on Tuesday, an Axios headcount found.Why it matters: The massive boycott represents a shift in American political norms as the party's grassroots have pressed lawmakers to be more partisan and less conciliatory towards Republicans.Several members of House Minority Leader Hakeem Jeffries' (D-N.Y.) senior leadership team were among the lawmakers who boycotted the speech, most notably Minority Whip Kathe...