The public’s opinion of politicians of both parties seems to have reached a new low. But no matter how much the voters detest Congress — or how justifiably — that does not mean that there will be radical changes at the next election.

For one thing, “Congress” is not on the ballot. Only individual members of Congress are. Most voters like their own Senator or Representative, often because of special favors that these incumbents have done for their own constituency — at the taxpayers’ expense.

Add to this the so-called “campaign reform” laws that restrict the raising of money that challengers need, in order to counter the millions of dollars’ worth of free advertising that incumbents get through ordinary media coverage, enhanced by the incumbents’ sponsoring of ever more legislation, expanding the role of government.

The very longevity of incumbents in Congress makes it expedient for them to treat each other as “facts of life” — people with whom you have to “go along to get along.” One of their common interests as incumbents is reelection. This can lead to all sorts of bipartisan log-rolling legislation to hand out the taxpayers’ money in ways that benefit incumbents of both parties.

In short, longevity in office can create more longevity in office. Moreover, this longevity can attract campaign contributions from special interests who expect something in return — if only a lightening up on government restrictions and red tape.

Many among the intelligentsia prefer to think of special interests as corrupting our dedicated public servants with campaign contributions. But Peter Schweizer’s new book, “Extortion,” shows what happens as the extorting of tribute by politicians in a position to do a lot of harm to businesses that do not pay them protection money.

Campaign contributions are just one of the things that can be extorted. The number of spouses, children or other relatives or favorites of Congressional incumbents who get high-paying jobs in private businesses regulated by government can hardly be coincidental.

When Al Gore was Vice President during the Clinton administration, he simply phoned various special interests and told them how much he wanted them to contribute.

If we are serious about countering this and other political games, at the country’s expense in both money and confidence in our government, we have to oppose the creation of a permanent class of long-serving politicians in Washington.

A one-term limit would simultaneously limit how long special interests could expect a pay-off from their campaign contributions. It would also limit, indeed eliminate, the need for millions of dollars of campaign contributions to stay in office.

Congressional reform should also include expanding the range of people likely to serve in Congress. Today, a successful engineer, surgeon, business executive, or even a full professor of economics at a leading university, would have to take a pay cut to serve in Congress.