Voters, take heart. You may be able to turn on your televisions and open your mailboxes this spring without being inundated with slashing political propaganda, at least from Democratic groups.

On Wednesday, Representatives Edward J. Markey and Stephen F. Lynch signed a pact designed to keep outside groups from running ads or sending mailers in their race for the Democratic nomination for US Senate. The so-called People’s Pledge aims to hold the candidates accountable for the messages voters receive and to limit the shadowy attacks that characterize modern political campaigns.