In his Aug. 24 op-ed, “2016’s Ralph Nader?,” Dana Milbank accused Green Party presidential nominee Jill Stein of making “more likely the singular threat of a President Trump.” He echoed legions of Democratic Party partisans who never think it is time for a progressive third-party presidential candidate to run because the Republican candidates are always worse. They use politically bigoted words such as “spoiler,” reserved for treating third-party candidates like second-class citizens. Many otherwise-tolerant reporters, columnists and editorial writers are quite okay with smaller candidates being obstructed in many ways, from ballot access to the debates.

Such discrimination counters a candidate’s civil liberties. Everyone has an equal right to run for public office. What kind of twisted logic insists that smaller-party competitors should forfeit their First Amendment rights to speak, petition and assemble freely? Dissent and resistance that attract voters historically have improved politics and achieved justice in our country.

Aren’t liberals pleased that earlier third parties — ballot access was easier in the past — and their voters rejected Mr. Milbank’s kind of advice? In 1840, the Liberty Party first opposed slavery. Later, new parties fought the exclusion of women from voting, asserted the rights of farmers and industrial labor and initiated calls for Social Security, unemployment compensation, minimum wages, health care for all and electoral reforms. They first put on the table most of the positive improvements from government.

Shamefully, the decaying Democratic Party works to block millions of voters from having a choice of progressive third-party candidates. No country in the Western world places more obstacles to third-party and independent candidates getting on the ballot than the United States. Democrats and Republicans built this exclusionary duopoly. As a result, major redirections and reforms, often supported by a popular majority, are excluded from electoral arenas. Without a competitive democracy, our political system cannot attract better candidates. A political monoculture with safe, gerrymandered incumbents serving myopic commercial interests is systematically undemocratic. It helps explain why the Democratic Party has been unable to defend this country from the worst Republican Party in history at the congressional and state levels.

Mr. Milbank justified his “don’t run, drop out” screed by referencing my campaign in 2000 as costing Democratic presidential nominee Al Gore the presidency. Were the Greens responsible for the absurd electoral college that threw an election? Mr. Gore won the popular vote handily. More than 300,000 registered Democratic voters in Florida voted for Republican nominee George W. Bush. Then-Florida Gov. Jeb Bush’s administration unlawfully purged thousands of Democratic voters from the state’s rolls, and Palm Beach County used deceptive butterfly ballots. The Florida Supreme Court’s mandated recount was blocked by a narrow conservative majority on the Supreme Court that then selected Mr. Bush as president. Why blame the Greens for these and other sine qua nons — absent any one of which Mr. Bush would have been denied the presidency?

Mr. Gore, who bore the brunt of a political coup from Tallahassee to the Supreme Court, has not scapegoated the Green Party. Scapegoating, besides debilitating its practitioners, has a grotesque and vindictive tail, harassing lawful competitors while ignoring self-renewal and external reforms. Ms. Stein will not abandon the Green Party’s resistance to Wall Street’s disastrous attack on our economy, the bipartisan expansion of the war-making empire and the bipartisan backing for bloated military and corporate welfare budgets that starve monies for public works and services. She opposes both parties, indentured to the craven demands of monied interests. Let’s stop the chronic censorious whining and work to secure fair, competitive elections for all candidates.

Ralph Nader, Washington