By Ted Hesson WASHINGTON (Reuters) – U.S. border officials are preparing for as many as 9,000 border arrests per day by the spring, according to two Department of Homeland Security officials, which would be significantly larger than last year’s peak and could cause a headache for the Democratic administration ahead of midterm elections. The number is a “worst-case scenario,” said one of the officials, both of whom requested anonymity to discuss internal planning. The administration of U.S. President Joe Biden grappled with a record-breaking 1.7 million border arrests last fiscal year, which en…