Let's say Reagan was successfully labeled as an extremist and voters gave President Carter another chance? How would the world have looked in the 1980s with no Reagan Revolution?
America would have been much worse off if Carter won a 2nd term. On the domestic front, the stock market and economic growth would have remained stagnant due to high taxes and regulations. In 1980, we had a supply problem with the labor force; due to to the extremely high marginal tax rates and bracket creep due to high inflation, people chose to either not work or stay in their current position rather than aspiring to move to a higher bracket. Reagan's tax cuts and deregulations liberated the American economy from years of liberal excesses. Reagan also appointed hundreds of conservative federal judges during his presidency, thus ensuring that an activist liberal agenda of the Warren and Burger courts did not continue unabated.
On the international front, although the Soviets would have collapsed eventually, Reagan hastened its demise through his drastic increase in military spending, supporting anti-communist dissidents throughout the world, and through his clarion call for human freedom. Reagan was a truly transformational President, whose influence will be felt for years to come. Unfortunately, we have not had a great man like him as President since.