Politics is largely about signals - messages to an enormously complex electorate that a candidate is one of them. But there are big messages and little messages - and the Democrats may still be concentrating too much on the latter.
The Democrats communicated with two American political subgroups this week, the rather small John Anderson crowd of independents and moderate Republicans, and the more substantial Jesse Jackson following among blacks. Mr. Anderson, who basked in a protest vote against Jimmy Carter and Ronald Reagan in 1980, has never really had a constituency of his own; he has wandered from campus to campus, a political John the Baptist, speaking with moral fervor on issues like arms control. Anderson's appeal is much like that of Gary Hart, who seems to have dropped from sight since his defeat at the party convention.
The Rev. Jesse Jackson is another matter. Polls show black Americans are 90 percent for the Democratic ticket, and still climbing. The issue is motivation and turnout. Most Americans would no doubt be turned off by Mr. Jackson's bartering the support of his entourage for some seven demands, including top-level campaign appointments for blacks and major domestic and foreign-policy addresses by Walter Mondale on issues important to blacks. Jackson's pledge of ''broad based,'' ''deep and intense'' support was undercut by his reserving ''the right to challenge'' Mr. Mondale publicly.
Still, both Mr. Jackson and Mr. Anderson, with their more impassioned style, represent the direction the Mondale campaign must take if the Mondale-Ferraro ticket is going to offer Reagan-Bush a serious challenge.
It helps the Republican ticket to portray Americans as self-satisfied - relishing material prosperity, patriotism, and confident assertiveness abroad.
But this is not an entirely smug electorate.
The American public feels it was burned too many times before on the big issues of the economy and foreign policy. A decade ago the effort to quash inflation led to ''stagflation,'' a new economic hybrid: inflation plus unemployment. Now inflation has been reduced to 4 percent. But interest rates are inexplicably high: they affect farmers, homeowners, small-business people, young householders who still aren't sure the American dream of owning a home is coming to them. Ballooning interest payments on the federal debt promise to eat up any margin for government spending on domestic programs.
The underlying economic challenge shifts, changes form; it hasn't gone away. The public perceives this. Mr. Reagan would be somewhat more vulnerable if the prime rate rises before the election and Americans believed the administration's economic policies were to blame.
Mr. Mondale's challenge is to start making 1984 look like a competitive race.
The Democrats are not yet seen, by their own candidates and operatives in the field, as being on the offensive this time around. Leading Democratic figures are not enthusiastic about the top ticket's performance thus far. They are making minimal appearances in its behalf. Those in Senate and House races are looking for ways to run on their own if Mondale and Geraldine Ferraro do not soon catch on with the public.
The Republicans did not make the best use of their convention's potential. They came across as too negative; they should have reached out more. The White House plans to hold a Hubert H. Humphrey Day early next month, inviting Mondale and Ms. Ferraro. This is signal-sending, too - for the support of Humphrey Democrats like UN Ambassador Jeane Kirkpatrick, who favor a stronger defense but also a more generous social-program thrust.
Such gestures could help the Republicans look more inclusive, to defend against the equity issue - the impression they favor the well-to-do, an impression the Dallas convention did little to dispel. Here too the Mondale-Ferraro ticket has an opening to argue that it offers an alternative economic program, a different slice of the American electorate it would stand up for.
The Democrats' task is to interest American voters in the advantages of changing the nation's leadership. Assistance from subgroup spokesmen like Anderson and Jackson can help. But it's really up to Walter Mondale to convince the main sweep of American voters of this, and motivate them to go to the polls in his party's behalf.