from the tisch wnet studios at lincoln center in new york, megan thompson. >> thompson: good evening, and thanks for joining us. president donald trump is marking his 100th day in office with a visit and rally tonight in a key swing state that propelled him to the white house. mr. trump is expected to address supporters in harrisburg, the capital of pennsylvania, which backed him last november, the first time the state went republican since 1988. before the rally, the president was set to visit a shovel and gardening tool manufacturer and sign an executive order directing the commerce department and u.s. trade representative to identify trade agreement violations by other countries and recommend solutions within six months. earlier, in his weekly address, the president touted his record on saving jobs and bringing change to washington. >> the most fundamental change can be found in the relationship between the people and their government. for too long, politicians cared more about special interests than they did about a very successful future for all americans. they took our taxpayers

in tonight's signature segment, newshour weekend's megan thompson reports on an effort to improve those numbers, and whether partisan politics could spoil the objectivity that scientists bring to policy debates. >> he's probably going to be in charge of yard signs because she has the biggest garage. >> reporter: on thursday morning, around 80 people filled a hall in washington, d.c., for lessons in campaigning for local school board, state legislature and even u.s. congress. >> when you're running for office for the first time... >> reporter: the agenda covered fundraising, messaging and recruiting volunteers, with political veterans like joe trippi, a high-profile democratic campaign consultant. >> the hunger's definitely there. the energy's definitely there. >> reporter: but this crowd wasn't typical activists; they were scientists and engineers who say the trump administration and republican-led congress have a hostile attitude toward science, especially when it comes to addressing climate change. >> we really need people with pro-science backgrounds to get involved. >> reporter: the