THE DEMOCRATIC presidential candidates offer a powerful rebuke of the vulgar, demeaning Republican presidential campaign — not so much in what Hillary Clinton and Bernie Sanders say about the Republicans, but simply in the way they behave. You wouldn’t mind your children watching their debates, which have been focused largely on policy. Both the former secretary of state and the Vermont senator offer serious, testable proposals. Both show respect for each other, for the voters and for the office they seek.

Take, for example, the fundamental question of how a government should tax and spend. Ms. Clinton in particular has offered a raft of serious, progressive proposals that are grounded in reality, even though the electorate has sometimes seemed more interested in ideological pizzazz. The independent Tax Policy Center, which has been examining each candidate’s fiscal plans, reported last week that Ms. Clinton’s would raise about $1.1 trillion in new revenue over a decade, almost entirely from very high earners. She would spend a significant portion of this money — on a tax cut for the middle class, making college debt-free and other programs. Though it is still unclear exactly how much of Ms. Clinton’s new revenue would be put to righting the country’s long-term budget outlook, hers is the most fiscally responsible plan on the table.

Mr. Sanders also claims to pay for all the new spending he proposes. But he would increase taxes — mostly on the wealthy, but on everyone to some extent — by a whopping $15.3 trillion over 10 years. The revenue would go to making college and health care free, among other goals. But the tax hikes would be so large and the spending requirements of his new programs so uncertain that the analysts warn that the plan carries economic risks that they cannot measure. There is little precedent for increasing the size of government so much and so fast.

The Republicans lately have not been much interested in discussing such matters. But they all have made proposals — and none of them passes the laugh test, as the Tax Policy Center analyses show.

Unsurprisingly, Donald Trump’s plan would do the most damage, reducing federal revenue by $9.5 trillion over 10 years. Ted Cruz takes the silver medal for irresponsibility, reducing revenue by $8.6 trillion, and Marco Rubio claims the bronze with a mere $6.8 trillion reduction. Each plan would require “unprecedented spending cuts” to work — on the order of slashing the entire defense budget or greater.

True, the estimates do not assume miraculous levels of economic growth, which Republicans typically rely on. But they also do not count the additional interest the country would have to pay if GOP tax cuts ended up being deficit financed. Congress has a much easier time cutting taxes than it does reducing spending, and there is little reason to believe a President Trump or a President Cruz could magically upend that pattern.

This, then, is the state of the presidential race: a thoroughly unbecoming campaign on the GOP side and a quieter but nevertheless stark contrast of visions on the Democratic side. It is clear who knows what running for president should look like — and who does not.