Graham Platner, a 40-year-old Army and Marine veteran who served four combat tours in Iraq and Afghanistan, launched his campaign for the Senate in Maine on Tuesday, joining a growing Democratic primary field seeking to take on Republican Sen. Susan Collins. Our next MSNBC Live event is on October 11th in New York City! Buy Tickets now: msnbc.com/live25 For more context and news coverage of the most important stories of our day click here: https://www.msnbc.com/ » Subscribe to MSNBC: https://