UPDATE 1-Immigrants march in U.S., but rallies lose steam

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By Dan Whitcomb and Syantani Chatterjee

LOS ANGELES, May 1 (Reuters) - Thousands of immigrants marched through cities across the United States on Thursday, but smaller crowds suggested their cause had lost momentum in this election year.

Immigration-rights activists have retrenched to focus this year's rallies on stopping workplace raids after Washington failed last year to act on reforms that included a path to legal status for illegal immigrants.

In Los Angeles, an estimated 8,000 people converged on City Hall. But the numbers were nowhere near the