Forecasters are increasingly optimistic the U.S. economic expansion could continue beyond the 2020 presidential election, aided by Republican tax legislation that is expected to lift growth over the next several years.

The slow-but-sturdy expansion that began in mid-2009 already is the third-longest in U.S. history and, if it continues into the second half of 2019, will exceed the 10-year record set by the 1990s economic boom.

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